Samples studied in science and industry are typically subject to a variety of different processing operations including imaging, material analysis, and modifying the sample. For example, a sample may be polished, coated with carbon, and then bombarded with an electron beam in a scanning electron microscope (SEM) to analyze the sample composition and to form a magnified image. The tools that are used for these steps are typically stand-alone tools, that is, tools that are purchased separated, typically from different manufacturers, and that are not connected to each other. Thus, moving samples between tools is done manually or using awkward add-on robotics. For example, a polishing machine can be used to polish a sample. The sample is then removed from the polishing machine, cleaned, and manually placed into an evaporator for deposition of a carbon layer onto the sample. The sample is then manually removed from the evaporator and placed into an electron microscope for observation.
Besides inefficient material handling, another difficulty with using stand-alone tools is the lack of a common coordinate system. When a microscopic feature is identified on a sample in one tool, it can be time consuming to locate the same feature on a different tool. Similarly, when a measurement or analysis is performed on one tool, it can be difficult and time-consuming to correlate that information with information from a different tool. For example, it may be desirable to use a first tool to measure the topography at one spot on the sample, use a second tool to determine the composition at the same spot, and then correlate the composition data with the topography data. Because the two tools have unrelated coordinate systems, aligning the measurements from the tools can be difficult.
Some processes, such as scanning electron microscopy and focused ion beam etching, require that the sample be maintained in a vacuum in a sample chamber. The typical method for moving a sample into and out of the sample chamber is to slowly vent the chamber to the atmosphere and allow it to reach atmospheric pressure. The chamber is then opened, the previous sample is removed, a new sample inserted, and the sample chamber re-evacuated. The time required to vent the sample chamber to atmosphere and then to re-evacuate the sample chamber is significant and can preclude the use of vacuum tools in a fast-paced production line.
Several techniques have been proposed to allow a sample to be moved into or out of a vacuum chamber without opening the chamber. For example, U.S. Pat. No. 4,080,526 to Kuhara et al. for “Electron Beam Machining Apparatus of the Dynamic Seal Type” describes a dynamic seal that permits a sample to be rotated into and out of a vacuum chamber without venting the vacuum chamber to atmosphere. U.S. Pat. No. 5,103,102 to Economou et al. for “Localized Vacuum Apparatus and Method” describes a multistage non-contact vacuum seal that allows movement between the vacuum chamber and a surface under observation. Similarly, U.S. Pat. No. 6,710,354 to Koch et al. for “Scanning Electron Microscope Architecture and Related Material Handling System,” describes a differentially pumped vacuum seal that provides a high vacuum in the center and successively lower vacuums toward the edge of the seal.
Another disadvantage of using stand alone tools is the expense of individual tools. A complete line of tools for sample processing, analysis, and imaging may require many expensive tools that are available only to well-funded laboratories. Still another disadvantage of using multiple stand alone tools is the amount of space required in a laboratory or a fabrication facility. Tools for microscopic processing are often located in clean rooms, and space within clean rooms is costly, both for construction and for maintaining the required cleanliness. The number of tools, and therefore the expense, can be reduced if multiple tools are combined in a single tool. Such multi-functional tools are known, but the integration of functionalities typically compromises the performance level of each of the functions.